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3rd International VLBI Technology Workshop , JIVE 10-14 Nov. 2014

The Development of Broadband VLBI Technologies in SHAO. Xiuzhong ZHANG xzhang@shao.ac.cn Shanghai Astronomical Observatory, CAS. 3rd International VLBI Technology Workshop , JIVE 10-14 Nov. 2014. Following VLBI 2010 project, SHAO started to study broadband VLBI tech.

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3rd International VLBI Technology Workshop , JIVE 10-14 Nov. 2014

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  1. The Development of Broadband VLBI Technologies in SHAO Xiuzhong ZHANG xzhang@shao.ac.cn Shanghai Astronomical Observatory, CAS 3rd International VLBI Technology Workshop , JIVE 10-14 Nov. 2014

  2. Following VLBI 2010 project, SHAO started to study broadband VLBI tech. • There are several groups working on the broadband VLBI tech. in SHAO • After long time discussion, SHAO decided to build a VGOS station by self-raised funds at Sheshan, near Shanghai. • This decision push SHAO engineers to work on the broadband VLBI tech.

  3. Talk of Bill Petrachenko

  4. Talk of Bill Petrachenko

  5. Cryogenic Front End QRFH • One set QRFH and LNA from Caltech • Design and develop Cryogenic system with cooperation of industry • Study the measurement methods of performance of broadband cryogenic receiver Low Noise Amplifiers

  6. Up Down Converter • Many companies are interest to help us to develop UDC for our VGOS station • Main specification: • Input : 2 – 14GHz (with linear polarizations) • Output: 512~1024 / 70 ~ 1024MHz selectable • Programmable with 0.1 MHz step Prototype System of UDC

  7. CDAS-2 With the new platform, CDAS2 with PFB (Poly-phase Filter Bank) algorithm is under testing. Now it can work in two modes: • 512 MHz Dual IF Mode: For each IF, it has – 512 MHz bandwidth input – 16 channels output – 32 MHz bandwidth for each output channels • 1024 MHz Single IF Mode : – 1024 MHz bandwidth input – 16 channels output – 64 MHz bandwidth for each output channels

  8. Labor test and real observation: Use SH25M and TM65 2 hours test observation in July to check functions of CDAS2 Flux (@ X band): 4C39.25 10.0Jy 0902+490 0.27 Jy SNR (Int. Time 2.048 s): 34.2 for 0902+490 1122.6 for 4C39.25

  9. CDAS-2 in the rack Team Leader: Zhu Runji

  10. MK6 Disk Array Two set MK6 system are already arrive in Shanghai Doing test with CDAS-2 now

  11. Calibration and time System • Pcal, Tcal and Dcal are in developing • Time/Frequency: shared with current system • Meteorological system: shared with current system

  12. Main Specifications of Antenna • Diameter: 13m • RF frequency range: 2-14GHz, upgradable to Ka band • Polarization: Linear polarizations • Optics: Ring focus • Aperture efficiency: >50% • Surface accuracy: <0.3mm • Pointing accuracy：<18” • Slew rate: az 12o/s, 3o/s2 ; el 6o/s, 3o/s2 • Slew range: az -270o~+270o; el 0o~90o • Reference point stability: ＜0.3mm • Signal path length stability: ＜0.3mm

  13. Ang Project Leader: Dr. Wang Guangli

  14. Antenna • There are two companies are interest to help us to develop VGOS antenna. • Both of these two companies have capacity to develop VGOS antenna. • SHAO should select one of them and sign antenna contract in near future

  15. RFI Measurements at Sheshan 1-2GHz

  16. 2-4GHz

  17. 4-8GHz 8-12GHz

  18. The RFI occurs in S-band. It is difficult to use continues broadband at S-band for VLBI observations. The Superconducting Filter is planned to use for the reduction of the RFI effects.

  19. Some Words for Correlator The way to develop the Correlator : Platform Selection: Software, PC based, GPU based more power consumption, need high speed inter-connect between PCs Hardware, FPGA based need long time to develop the firmware need more libraries to reduce the developing time Hybrid, FPGA used as HPC, others with PCs not so more power consumption reduce the developing time

  20. Hybrid, FPGA used as HPC, others with PCs

  21. Correlator System Control Data Buffer (Playback) Main Spec. (one Uniboard): 4 Stations, 2Gbps/ Station UniBoard & Power supply Many thanks for the helps of JIVE and ASTRON UniBoard team! Team Leader: Xu Zhijun

  22. Summary • The electronics part of Sheshan VGOS station will be completed in near future • Sign Antenna contract as soon as possible • Cryogenic Receiver design and development • Improve the performance of UDC and DAS • Broadband test observation with current big antenna • Study of the structure of the Correlator

  23. Thanks!

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